I have a a 10 year old Kohler Taboret widespread sink faucet (K-8211) that behaves like it has a bad pressure balancer. Looking at the diagrams on the Kohler web site, I don't see anything that suggests the faucet even has a pressure balancer function. This is a sink valve not a shower valve.

Does anyone know what might be going on? I can turn the hot water on in the morning and it runs fine until the hot water arrives. Then the flow slows down to a trickle. I can open the cold water and the pressure returns but I get lukewarm water.

It does NOT have a PBU, and if it did, it would only change the hot water pressure to match the cold, but you DO have cold pressure so that is not the problem. There are temperature specific problems, such as expanding rubber washers or brass stems, but we would have to be there to diagnose those problems.

My guess would be a loose washer. This happens at times if the seat is bad and grabs the washer, which can twist the washer and the screw along with it. If the washer is gouged, change the seat. Thats my guess, but, like HJ said, there are other possibilities.

One other question tho - could it be the ceramic cartridge itself? I replaced it 3+ years ago.

I have a clearer explanation of the behavior (after shaving this morning). I can open the faucet
full and the flow is normal. At first, it takes about a minute for the flow to slow down - to about
half - not a trickle. Then, if I shut it and open the faucet again, it runs full for about 1 second
then slows again.

If it is not the cartridge, then it would have to be in the piping, or the connection between the faucet and the spout, which would be very unusual. However, if the hose between the faucet and spout is kinked, that symptom could occur as it expands and contracts making he kink bend and shut off the water.

Your amazing Terry!!! That's exactly what it was. I didn't replace the valve. I just opened it up all the way. I must have left it half open when I changed the cartridge. Thanks to all who helped with suggestions.